(c) When a boat is required to give mark-room
by rule 18.2(b),
(1) she shall continue to do so even if later an overlap
is broken or a new overlap begins;
(2) if she becomes overlapped inside the boat entitled to mark-room,
she shall also give that boat room to sail her proper course while they remain
overlapped.

(d) Rules 18.2(b) and (c) cease to apply when the boat entitled to mark-room
has been given that mark-room, or
if she passes head to wind or leaves the zone.

(e) If there is reasonable doubt that a boat obtained or broke an overlap
in time, it shall be presumed that she did not.

(f) If a boat obtained an inside overlap
from clearastern
or by tacking to windward of the other boat and, from the time the overlap
began, the outside boat has been unable to give mark-room,
she is not required to give it.